SYNTHESIS OF ZEOLITE ZSM-5 AT LOW TEMPERATURE AND ITS MODIFICATION TOWARD FIBROUS MORPHOLOGY WITH ULTRA-HIGH SURFACE AREA
Diffusion limitation, especially for the bulky molecules, due to the small micropores (around 0.55 nm) is the main problem of the role of ZSM-5 as a catalyst. This limitation induces the diffusion-determining reaction so that the reactants cannot access all of the active sites. Besides that, this di...
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| Format: | Theses |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/22305 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Diffusion limitation, especially for the bulky molecules, due to the small micropores (around 0.55 nm) is the main problem of the role of ZSM-5 as a catalyst. This limitation induces the diffusion-determining reaction so that the reactants cannot access all of the active sites. Besides that, this diffusion limitation can also provoke the formation of cokes, for instance in catalytic cracking, which may deactivate the catalyst in a short time. In order to overcome this problem, one will need additional porosity, either mesopores (2-50 nm), macropores (>50 nm) or both of them, which can be achieved by tailoring the morphology. In this research, we did the synthesis of ZSM-5 with fibrous morphology and ultra-high surface area. At first, we synthesized ZSM-5 crystals at low temperature (90 °C) with a reduced amount of tetrapropyl ammonium ions (TPA+/Si = 0.04), so called LT-ZSM-5. SEM images showed that LT-ZSM-5 exhibited a spherical-like morphology. N2 adsorption-desorption and TEM showed that LT-ZSM-5 possessed mesopores which are originated from aggregation of smaller ZSM-5 crystals. Through reverse-micelles method, with cetyltrimethyl ammonium bromide (CTABr) as surfactant, the external surface of LT-ZSM-5 could be successfully modified to fibrous morphology, so called Fi-ZSM-5, with BET surface area of 565 m2/g. This is categorized as ultra-high surface area since its value is more than 500 m2/g. From SEM image, we could observe additional macroporosity with pore size more than 50 nm on the external surface of Fi-ZSM-5. This means that ZSM-5 with complete porosity could be achieved and is expected to overcome the diffusion limitation and significantly enhance the catalytic performance of ZSM-5. |
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